Widespread White Matter DTI Alterations in Mesial Temporal Sclerosis Independent of Disease Side

Purpose: The aim of this study was to evaluate white matter (WM) integrity in vivo in patients with unilateral mesial temporal sclerosis (MTS).

Methods: Diffusion tensor imaging (DTI) findings from patients with left-sided MTS (L-MTS; N = 14) and right-sided MTS (R-MTS; N = 13), all taking antiepileptic medication, were compared with those from gender- and age-matched controls; DTI was performed along 30 noncollinear directions in a 1.5-T scanner. Tract-based spatial statistics (TBSS) analysis was performed by creating a WM skeleton; 5000-permutation-based inference (threshold, p < 0.05) was used to identify fractional anisotropy (FA) abnormalities. Mean (MD), radial (RD), and axial diffusivities (AD) were projected onto the mean FA skeleton.

Results: Compared with the control groups, patients with MTS had decreased FA affecting widespread WM tracts as well as extensive areas with increased RD, bilaterally and independent of the disease side. Areas with decreased FA and increased RD overlapped substantially. There were no significant differences in DTI parameters between L-MTS and R-MTS patients.

Conclusion: Diffusion tensor imaging abnormalities were observed within and beyond the temporal lobe in patients with MTS. Patients with R- and L-MTS had extensive bilateral abnormalities in comparison to controls. These findings suggest that MTS pathobiology involves diffuse dysfunction of WM tracts, even in areas with no direct connections to the hippocampus.